This invention relates generally to scroll compressors and more particularly to a control arrangement therefor for sensing low system gas charge and/or a reverse rotation condition.
Scroll machines generally comprise first and second scroll members, each comprising ar end plate which is provided with an upstanding spiral wrap. The scroll members are interleaved, with the flanks of the wraps engaging one another at substantially line contacts and the tips of each wrap sealingly engaging the end plate of the other scroll member so as to define travelling pockets of varying volume in which gas is compressed as one scroll member is caused to orbit relative to the other. Suction gas is communicated to the outermost compression chamber near the radially outward-most portion of the wraps and discharged through a discharge port centrally of the wraps. A motorized drive mechanism causes the orbiting scroll to orbit thereby decreasing the volume of the pockets and increasing the pressure of the compressed gas as it is progressively moved towards the discharge port. Exemplary of such an apparatus is U.S. Pat No. 4,767,293 entitled "Scroll Type Machine", the disclosure thereof being specifically incorporated herein by reference.
When a scroll machine works as a compressor, the pockets are pressurized thereby causing the scroll members to be forced apart, however when orbited in the reverse direction the machine acts as a vacuum pump and therefore the scroll members are drawn together. The latter can be caused when the motor is improperly wired, or by a power interrupt, and the resulting vacuum can cause damage to the scroll members because of the excessive wear which occurs. The possibly destructive vacuum condition can also occur when a serviceman runs the compressor with the suction blocked, a not uncommon occurrence.
Another condition which can result in excessive wear is a loss of charge, particularly in a refrigerant compressor, which results from the installation of insufficient refrigerant into the system or from refrigerant leakage.
It is therefore a primary object of this invention to provide a control for a scroll-type machine which overcomes the aforesaid problems in a simple and inexpensive manner, and which does not result in any significant loss of efficiency.
Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims taken in conjunction with the accompanying drawings.